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Old February 16th 04, 08:02 PM
Steve Nosko
 
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Not really, Jim...unless you mean something special by "nonlinear
multipliers" like diodes/varactors which I suspect fall under your comment.
In the two-way radios of the 60's & early 80's before synthesizers, I
designed many a single stage multiplier of 2x or 3x, which were preferred
and sometimes 4x. They worked very well...using cap input coupling, to keep
the base Z low at the harmonics and keeping the conduction angle optimized
for output level. Also, the adjacent harmonics are easier to filter than
higher orders of multiplication (when that is a factor. Only a single
resonant circuit was required between stages.
The bottom line depends upon the spurious requirements. Then there are
always preferences for what we may have used in the past - and what the
application actually is.
Starting with a spectral comb(like a square wave or other pulse-type
waveform) and picking off the desired harmonic can also be very effective,
but again, it depends upon the specific application.
I did a synthesizer mixer with no tuned circuits to get from 40 MHz
crystal oscillator to 220MHz to mix down a VCO to an IF for the programmable
divider. Was really sweet! Did the same for what I believe was the very
first synthesized 2M hand held in 1973. A Motorola HT220. Even had the
Transmit VCO _ON_ yes _ON_ the TX frequency. Total current drain was 7ma.
Tx spurious (-70dBc) better than the original (-35-40dB) Still have it.

--
Steve N, K,9;d, c. i My email has no u's.

"Jim Thompson" wrote in message
...
On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote:

I think it boils down to something very practical:
...It becomes a matter of how close and how large the
undesired spectral components are compared to the desired spectral
components. ...
As an example, a x4 multiplier stage will have a desired output at Fin x

4,
and close-in undesired products at Fin x 3 and Fin x 5. ...
Joe, W3JDR

[snip]

I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers.

...Jim Thompson